An FBI agent is forced to work with an institutionalized scientist and his son in order to rationalize a brewing storm of unexplained phenomena. The third and fourth seasons take place in dystopian futures.
An ex-assassin and a wealthy programmer save lives via a surveillance AI that sends them the identities of civilians involved in impending crimes. However, the details of the crimes--including the civilians' roles--are left a mystery.
A warrior from the 16th Century, the first female university student from the 19th Century, and a paramedic from the 21st Century join a secret agency to prevent people from changing Spanish history using time-traveling doors.
The disappearance of a decorated FBI agent's wife leads him to a secret government unit assembled to hunt a group of ruthless terrorists - shadowy figures that may or may not be from this world.